1. Field of the Invention
This invention concerns a method of manufacturing a heat sink made of aluminum in which a plurality of fins are brazed on a heat dissipating substrate.
2. Related Art Statement
In electronic equipments such as computers and NC control equipments, many heat generating devices are incorporated and various kinds of heat dissipating members are used in order to rapidly release the generated heat and maintain the normal operation for a long time. A heat sink made of aluminum in which a plurality of thin plate-like fins are attached on a heat dissipating substrate is one of such heat dissipating members. Further, in view of the material, 1000 series aluminum excellent particularly in thermal conductivity is often used and 3000 series or 5000 series aluminum is used in the case of requiring high strength.
Further, in the heat sink of the shape described above, it is important to enlarge the heat dissipating area in order to improve the heat dissipating performance and, for this purpose, it is necessary to reduce the thickness of the fins and narrow the distance between the fins thereby increase the number of fins.
However, since 3000 series or 5000 series aluminum is inferior in the thermal conductivity to 1000 series aluminum, heat sinks in which fins of a reduced thickness are formed of such materials for ensuring the strength involve a problem in the heat dissipating performance. Further, when the fins of reduced thickness are formed of 1000 series aluminum having good thermal conductivity, they result in a problem that they are liable to be broken by vibrations or impacts upon handling.
An object of this invention is to provide a method of manufacturing a heat sink made of aluminum having both high strength and heat dissipating performance together in view of the back ground art as described above.
For attaining the foregoing object, this invention provides a method of manufacturing a heat sink made of aluminum by brazing a plurality of fins 13 on a heat dissipating substrate 11, in which the fin 13 comprises an Alxe2x80x94Mgxe2x80x94Si series alloy containing from 0.3 to 0.7% by weight of Mg, from 0.3 to 0.7% by weight of Si and the balance of Al and inevitable impurities, cooling is conducted in a cooling process after heating for brazing at a rate of 50xc2x0 C./min or higher in a range from 450-500xc2x0 C. to 300xc2x0 C. and then artificial aging is applied at 100 to 250xc2x0 C.
The Mg content in the Alxe2x80x94Mgxe2x80x94Si series alloy constituting the fin 13 is preferably from 0.4 to 0.6% by weight.
The Si content in the Alxe2x80x94Mgxe2x80x94Si series alloy constituting the fin 13 is preferably from 0.4 to 0.6% by weight.
Further, cooling after the heating for brazing is preferably conducted at a rate of 75xc2x0 C./min or higher.
Further, the artificial aging is applied preferably at 160 to 220xc2x0 C.
Further, brazing between the heat dissipating substrate 11 and a plurality of fins 13 are preferably conducted by using an Alxe2x80x94Si series alloy brazing material and a chloride series flux in an inert gas atmosphere while heating at 577 to 610xc2x0 C.